``The Chinese Gold & Silver Exchange Society (CGSE), based in Hong Kong, aims to launch a physical bullion trading exchange and a 1,500-tonne depository in mainland China within the next year, its president said on Thursday. The century-old firm, which runs Hong Kong's only physical bullion trading exchange, is looking to tap the burgeoning demand for gold in China, which last year toppled India from its ranking as the world's top gold consumer. ''